共查询到20条相似文献,搜索用时 15 毫秒
1.
Steady-state solutions of the output-feedback pumped bistable laser(OFPBL)have been obtained using the semiclassical laser equations.A linear-stability of the solutionshas been analysed.The results tell us that width of the hysteresis loop and the laser output in-tensity vary widely with the pump intensity and the intensity of input optical signal and thefeedback coefficient of the laser output as well as the other parameters.It shows that this typeof bistable laser is a kind of active optical bistable device which can be adjusted and controlledconveniently. 相似文献
2.
The structural,energetic and electronic properties of chiral(n,m)(3≤n≤6,n/2≤m≤n)single-wall copper nanotubes(CuNTs)have been investigated by using projector-augmented wave method based on density-functional theory.The(4,3)CuNT is energetically stable and should be observed experimentally in both free-standing and tip-suspended conditions,whereas the(5,5)and(6,4)CuNTs should be observed in free-standing and tip-suspended conditions,respectively.The number of conductance channels in the CuNTs does not always correspond to the number of atomic strands comprising the nanotube.Charge density contours show that there is an enhanced interatomic interaction in CuNTs compared with Cu bulk.Current transporting states display different periods and chirality,the combined effects of which lead to weaker chiral currents on CuNTs. 相似文献
3.
Structural,electronic,optical,elastic properties and Born effective charges of monoclinic HfO_2 from first-principles calculations 下载免费PDF全文
First-principles calculations of structural, electronic, optical, elastic, mechanical properties, and Born effective charges of monoclinic HfO2 are performed with the plane-wave pseudopotential technique based on the density-functional theory. The calculated structural properties are consistent with the previous theoretical and experimental results. The electronic structure reveals that monoclinic HfO2 has an indirect band gap. The analyses of density of states and Mulliken charges show mainly covalent nature in Hf-O bonds. Optical properties, including the dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, loss function, and optical conductivity each as a function of photon energy are calculated and show an optical anisotropy. Moreover, the independent elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, compressibility, Lam6 constant, sound velocity, Debye temperature, and Born effective charges of monoclinic HfO2 are obtained, which may help to understand monoclinic HfO2 for future work. 相似文献
4.
In this study, the electronic and the optical properties of monolayer black phosphorus (BP) doped with Gold (Au), Tin (Sn) and Iodine (I) atoms have been investigated by the density-functional theory (DFT) method. In the calculations, the electronic and the optical properties of monolayer BP have been substantially changed with doping. Monolayer BP has a narrow bandgap as 0.85 eV, BP doped with these atoms, results in a metallic behaviour and nearly spin gapless band gap behaviour. The dielectric constant of BP which shows anisotropic optical properties due to different edge states as zigzag and armchair has been changed with doping especially with Au. 相似文献
5.
Emmanuel Fromager 《Molecular physics》2013,111(5):419-434
The exact formulation of multi-configuration density-functional theory is discussed in this work. As an alternative to range-separated methods, where electron correlation effects are split in the coordinate space, the combination of configuration interaction methods with orbital occupation functionals is explored at the formal level through the separation of correlation effects in the orbital space. When applied to model Hamiltonians, this approach leads to an exact site-occupation embedding theory (SOET). An adiabatic connection expression is derived for the complementary bath functional and a comparison with density matrix embedding theory is made. Illustrative results are given for the simple two-site Hubbard model. SOET is then applied to a quantum chemical Hamiltonian, thus leading to an exact complete active space site-occupation functional theory (CASSOFT) where active electrons are correlated explicitly within the CAS and the remaining contributions to the correlation energy are described with an orbital occupation functional. The computational implementation of SOET and CASSOFT as well as the development of approximate functionals are left for future work. 相似文献
6.
7.
High contrast all-optical diode based on direction-dependent optical bistability within asymmetric ring cavity 下载免费PDF全文
We propose a simple all-optical diode which is comprised of an asymmetric ring cavity containing a two-level atomic ensemble. Attributed to spatial symmetry breaking of the ring cavity, direction-dependent optical bistability is obtained in a classical bistable system. Therefore, a giant optical non-reciprocity is generated, which guarantees an all-optical diode with a high contrast up to 22 d B. Furthermore, its application as an all-optical logic AND gate is also discussed. 相似文献
8.
对一种有着单重态和三重态的典型的有机物的四能级系统的光学双稳进行了研究。由密度矩阵的速率方程近拟推导出了光学双稳的状态方程。对单重态和三重态吸收或色散情况下的双稳情况用数值解的方法进行了讨论。文中分析了单重态和三重态的合作参数、原子失谐参数和腔失谐参数对双稳的影响。 相似文献
9.
10.
Optical bistability and multistability in a three-level Δ-type atomic system under the nonresonant condition 下载免费PDF全文
Under a nonresonant condition, we theoretically investigate hybrid
absorptive-dispersive optical bistability and multistability
behaviours in a three-level Δ-type system by using a microwave
field to drive a hyperfine transition between two upper excited
states inside a unidirectional ring cavity. We find that the optical
bistability and multistability behaviours can be controlled by
adjusting the intensity of the microwave field or the intensity of
the coherent coupling field. Furthermore, our studies show an
interesting phenomenon of the transition from the optical
bistability to the optical multistability only by changing the
negative detuning of the coupling field into the positive detuning
of the coupling field. 相似文献
11.
A. Cordelli 《Il Nuovo Cimento D》1994,16(1):45-53
Summary The use of modified Lanczos procedure to obtain the ground-state eigenvalue and eigenvector of the Hamiltonians of physical
systems and its subsequent modification for the determination of excited states has been revealed a very efficient and powerful
procedure. Nevertheless, when implementing the method, one notices that the convergence of the algorithm is very slow, so
that the calculation may become heavy from a computational point of view. The aim of this paper is the proposal of an accelerated-convergence
technique (which has already been successfully used in density-of-states calculations), that allows to obtain a faster convergence
of the modified Lanczos eigenvalues to the exact ones. The advantages of such a technique are shown through the discussion
of some examples. 相似文献
12.
We study the effect of a nearby phase-conjugate mirror (PCM) on the gap soliton of a Kerr non-linear periodic structure. We
show that phase conjugation of the gap soliton (in the sense of replication of the amplitude profile in the reverse direction)
is possible under the condition of PCM reflectivity approaching unity. This is in contrast with the results for linear structures,
where the wave profiles can be conjugated for arbitrary values of the PCM reflectivity. The sensitivity of the conjugation
of the gap solitons to PCM reflectivity is ascribed to the fine balance of non-linearity with dispersion, necessary for their
existence. 相似文献
13.
应用光学双稳原理的高精度光纤传感器 总被引:2,自引:1,他引:2
本文提出一种光纤干涉仪与光电混合光双稳装置相结合的新型光纤传感器.用光双稳开关脉冲计数度量温度变化,其测量精度比基于干涉条纹计数的一般干涉型光纤传感器的精度约高10~100倍,而且测量精度可调节.完成了这种传感器原理的模拟实验验证. 相似文献
14.
We study the influence of frequency noise on optical bistability in the neighborhood of the critical point where the hysteresis loop appears. We show that when the transmitted field evolves on a faster time scale than that of the noise, the hysteresis loop shifts toward lower values of the incident pumping field. 相似文献
15.
P. Cortona 《Il Nuovo Cimento D》1993,15(2-3):243-251
Summary The lattice parameter, the bulk modulus and the dissociation energy of NaCl and MgO are calculated by a method which allows
the direct determination of the total energy and of the charge density of a crystal. An extensive comparison with the results
of standard band structure calculations is reported.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
16.
反馈调谐CO2激光器的静态与动态行为 总被引:1,自引:1,他引:0
建立了反馈调谐CO_2激光器的物理数学模型.稳态分析结果表明,只有当反馈系数大于某一临界值之后,才能出现激光器泵浦速率与激光输出之间的光学双稳性.线性稳定性分析的结果表明,系统失稳的必要条件是失谐量的Debye弛豫速率(反馈系统的带宽)必须超过布居反转的衰减速率.只有当激光泵浦落在某一范围内时,才出现不稳性.数值分析的结果证明了系统输出倍的周期分岔混沌行为.线性稳定性分析预言的Hopf分岔频率与数值分析的结果符合得很好. 相似文献
17.
基于密度泛函理论框架下的第一性原理离散变分(DV)和DMol方法研究了4d过渡金属元素在γ-TiAl 中的择优占位行为及其Nb和Mo的合金化效应.转移能的计算结果表明Y,Zr,Nb,Mo在γ-TiAl中有Ti占位倾向,而Tc,Ru,Rh和Pb则表现为Al占位倾向.通过对差分电荷密度、Mulliken轨道集居数以及态密度的分析表明Nb和Mo可以提高杂质元素与其近邻基体元素之间的相互作用和相应原子之间的键合强度,导致较强的固溶强化效应.
关键词:
密度泛函理论
第一性原理
电子结构 相似文献
18.
Canio Noce 《Il Nuovo Cimento D》1991,13(3):343-361
Summary The effects of the shape of free conduction density of states on the physical quantities for the periodic Anderson model have
been investigated. 相似文献
19.
磁致伸缩光纤磁光光学双稳态 总被引:1,自引:0,他引:1
报道了一种基于磁致伸缩原理实现的全光纤结构磁光光学双稳态装置。与分立元件的磁光双稳系统相比较,该系统的双稳开关功率降低了2~3个数量级,实验结果与理论计算相符。 相似文献
20.
Density-functional theory study on the electronic properties of laves phase superconductor CaIr_2 下载免费PDF全文
In this work we have used density-functional theory methods such as full-potential local orbital minimum basis(FPLO) and ELK-flapw to study the electronic structure of newly discovered Laves phase superconductor CaIr_2.The calculation of density of states(DOS) indicates that the bands near Fermi level are mostly occupied by the d-electrons of iridium.The simulation of de Haas-van Alphen(dHvA) effect has been performed by using Elk code to check the Fermi surface topology.The results show that there exist four Fermi surfaces in CaIr_2,including two electron-type and two hole-type surfaces.The optical response properties of CaIr_2 have been calculated in the dipole-transition approximations combined with including intra-band Drude-like terms.In the optical spectrum σ(ω) shows that the crossover from intraband to inter-band absorption occur near 1.45 eV.Further analysis on the electron energy loss spectra(EELS) matches the conclusion from that of optical conductivity σ(ω). 相似文献